Use `thiserror` for strongly typed errors instead of `anyhow`

While anyhow is convenient for emitting human-readable errors, its errors are generally unsuitable for catching. We work around this by [nesting `Option` with `Result` in `receive_raw` and `receive_message`](https://github.com/fwcd/miracle/blob/b5e886a9de4a4e8490a54dde6a0a8ee8910a3377/src/client_handler.rs#L71), but this quickly becomes unergonomic and [returning a custom error as we do in `lighthouse-client`](https://github.com/ProjectLighthouseCAU/lighthouse-rust/blob/6791919d02af0a45b18a966bfcd1ae7936fa5525/lighthouse-client/src/lighthouse.rs#L111) might be a better idea.